The short answer of course is "very".

In a bit longer answer, it's certainly one of the better films in the MCU franchise, and certainly up with Guardians of the Galaxy for the fun factor, which is when I think Marvel is doing it's best is when it's having fun with the subject matter. There's so much going on, but it's great to see that there is still fun being had while still advancing plot (both internal and overarching) and characters.

And it's never not fun watching Goldblum chewing the scenery